The world's stockpile of munitions have several driving reasons for their safe and efficient destruction. These reasons vary from the obvious need for arms reduction since the end of the Cold War, to treaty obligations, the high cost of secure storage, to public risk near the storage locations, and to the fact that chemical munitions are slowly degrading. The degradation problem has become so bad that almost 6% of the items processed at the Army's destruction facility can not be processed with existing technologies. In addition, these munitions are potentially dangerous as the toxic nerve agents have corroded their containers and infiltrated the enclosed explosive bursters assembled within the weapons. This problem has become serious enough that the US Army's studies on chemical agent rockets have predicted that within the next few decades the units may auto-ignite due to degradation of internal stabilizers.
The conventional methods of accessing the munitions in this condition are inefficient at best, and dangerous at worst. Besides the previously mentioned 6%+ or more failure rate experienced by the Army using existing technology, more than three of the limited number of chemical munitions demilitarized have exploded during disassembly. Clearly the use of the current mechanical disassembly processes are both dangerous and inefficient.
An alternative munition accessing method that has had much publicity is the use of liquid nitrogen to chill the munitions below their brittle transition temperature and then to fracture the components into small pieces. Unfortunately, the massive volumes of liquefied nitrogen required and the length of time necessary to adequately chill the munitions preclude the process from being efficient. In addition, this process has also experienced an explosion during operation leaving some serious doubt about the process' safety.
One might conclude that use of high pressure waterjets would be the safest system for cutting casings as an initial step in the demilitarization of munitions. Unfortunately however, the chemical agents and explosives used by the militaries of the world are typically hydrophobic materials, like oils, that do not mix appreciably with water. Experience has shown that when a waterjet is used on explosives, a thick emulsion is formed that severely complicates further processing. An example of emulsions formed by water and hydrophobic oils is common mayonnaise, which closely resembles the explosive/water or chemical agent/water emulsions.
Besides being almost impossible to pump efficiently, such emulsions have other severe disadvantages. Many of the military energetics are still dangerous in their water emulsion form. This characteristic is heavily exploited by the commercial explosive industry where emulsion explosives are commonly used materials for rock blasting. The pumping of explosive emulsions increases the danger to plant operations because the emulsions plug piping, deposit explosives throughout the plant piping, and can easily propagate an explosion from one part of the plant throughout the rest of the facility. Finally, the use of water to form explosive or chemical agent emulsions reduces the effectiveness of the decontamination materials as the emulsions form stable droplets that restrict the diffusion of the decontamination chemistries to their targets.
Alternative fluids to water have been suggested in connection with specialty fluidjet cutting operations. In this regard, hydrocarbon solvents may be used when highly reactive alkali metals, like lithium or sodium are being processed.
U.S. Pat. Nos. 4,854,982 (Melvin et al I) and 5,284,995 (Melvin et al II) disclose pressurized anhydrous liquid ammonia in demilitarization procedures. More specifically, Melvin et al (I) disclose methods for demilitarization of rocket motors containing solid and ground composite propellant comprising ammonium perchlorate oxidizer and other miscellaneous ingredients. The propellant composition is removed by mean of a spinning spray type nozzle which discharges pressurized anhydrous ammonia directly into the interior of open rocket motor cases to erode or reduce the propellant to small particles. A slurry mixture accumulates in the rocket motor casing consisting of dissolved oxidizer and other residual propellant ingredients as insolubles. The slurry is further treated, e.g., by filtration. Recovery of the oxidizer occurs when the ammonia is allowed to gasify causing the ammonium perchlorate to drop out of solution. The ammonia used in the wash out process is dried and recompressed for reuse in the process.
Melvin et al (II), as in the case of Melvin et al (I), also employs a pressurized spray of anhydrous liquid ammonia, but they use it to extract and recover nitramine type oxidizers from solid rocket propellants, in particular, those known as "HMX" and "RDX", or cyclotetramethylenetetranitramine and cyclotrimethylenetrinitramine, respectively. Melvin et al (II) employs a sequence of steps for rocket motor demilitarization by propellant extraction, separation and recovery. They begin with the direct removal of the solid propellant. One method used is mechanical cutting and comminution and/or liquid jet ablation with pressurized ammonia spray nozzles. Alternatively, a comminution fixture may be used with pressurized liquid ammonia spray. In either embodiment, the spray nozzle or comminution fixture is placed in the interior of an open rocket motor and pressurized ammonia discharged against the propellant. The solid propellant is fractured or comminuted, reduced to smaller particles and removed from the motor in the form of a slurry for further treatment.
Melvin et al (II) also disclose bulk propellant from sources other than rocket motors macerated in a dedicated pressure vessel. In this embodiment, chips of propellant can be further treated by spraying the interior of the pressure vessel with a high pressure ammonia jet pre-treatment before introducing the material into an extractor/separator system.
While the methods of Melvin et al (I) and (II) are useful in the removal and recovery of chemical propellant from rocket motors, their methods have limited applications because they are dependent on a suitable access opening in the munition, such as a rocket nozzle or port, or at least partial disassembly of the munition in order to introduce the required ammonia spray nozzle or modified fixture for direct spraying of the propellant. The disadvantage of such methods is that to access an otherwise closed casing or containment for demilitarization by interior spraying, disassembly or other processing of the munition is required. However, disassembly is a slow, inefficient process, and therefore, non-economic. More importantly, mechanical disassembly of munitions is hazardous. For example, an M55 rocket is a chemical warfare munition containing approximately 10 pounds of highly toxic nerve agent, more than 2 pounds of dangerous explosives and about 19 pounds of reactive rocket propellant. Various systems for cutting casings of munitions have been tested including the use of commercial waterjets. In addition to the reasons outlined above concerning the potential hazards associated with aqueous emulsions of chemical agents and energetics, their extraction, recovery and recycling from aqueous effluents has also proven to be economically unattractive.
While the methods of Melvin et al (I) relate to the recovery of propellants, and Melvin et al (II) also relates to recovery and in some instances to the destruction of select high energy ingredients with ammonia, neither of the Melvin et al patents teach or suggest methods which will be suitable for the destruction of all or virtually all classes of hazardous substances, particularly energetics and chemical warfare agents, using protocols that are fully compatible with ammonia-containing effluents.
Accordingly, there is a need for more efficient, cost effective methods with an improved margin of safety for the demilitarization of munitions and ordnance, and in particular all classes of chemical warfare agents, energetic materials, and combinations thereof, as well as most other hazardous chemical substances, and substrates contaminated with hazardous materials. Such methods should include the preliminary step of accessing interiors of containments for the above substances and substrates by means of high pressure fluidjet cutting with a liquid capable of providing improved cutting efficiency, and which is fully compatible with process steps, as may be needed, in demilitarization and chemical decontamination protocols.